Variable ratio rotary drive mechanism and wheel chair embodying same

ABSTRACT

A variable ratio rotary drive mechanism is provided for wheel chairs and other uses. The drive mechanism has a pair of concentric driving and driven members defining an intervening annular space containing a variable ratio gear train which drivably couples the members, whereby rotation of the driving member drives the driven member in rotation. A shift lever is provided for operating the gear train to vary its ratio and thereby the mechanical advantage of the drive mechanism. A wheel chair is provided having wheel assemblies embodying the rotary drive mechanism to permit adjustment of the force which the occupant of the chair must exert on the wheels to propel the chair.

United States Patent Inventors Reuben V. Sasse 703 Verde Vista, Pomona,Calif. 91767; John A. Charvat, 1138 West B St.,

Patented Feb. 16, 1971 VARIABLE RATIO ROTARY DRIVE MECHANISM AND WHEELCHAIR EMBODYING SAME 2 Claims 6 Drawing Figs ABSTRACT: A variable ratiorotary drive mechanism is pro- U.S. Cl. 280/230; vided for wheel chairsand other uses. The drive mechanism 74/789; 280/238. 280/242, 280/249has a pair of concentric driving and driven members defining Int. Cl.562m 1/16, an intervening annular space containing a variable ratio gearB62m 11/16; F16h 57/ 10 train which drivably couples the members,whereby rotation Field of Search 74/789; of the driving member drivesthe driven member in rotation. A 280/242, 248, 236, 238, 230, 249 shiftlever is provided for operating the gear train to vary its ratio andthereby the mechanical advantage of the drive R r C1 d mechanism. Awheel chair is provided having wheel asseme erences l e blies embodyingthe rotary drive mechanism to permit adjust- UNITED STATES PATENTS mentof the force which the occupant of the chair must exert 605,530 6/1998Way 280/238 on the wheels to propel the chair.

q 562 /4 54 z 24 54 v 5 24 4t w l I E [6 6 ---r 46 PATENT ED FEB] s 1971I sum 1 BF 2 R V v, mm f @5 m WMA. m .MN M 5 0 i a slssalssaIPATENTED'FEBIBIHYI SHEET 2' 0F 2 lNVE/VTORS REueE/v M 6/1555 Jay/v A,CHAR ATTORNEY VARIABLERATIO ROTARY DRIVE MECHANISM AND WHEEL CHAIREMBODYING SAME BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates generallylto rotary drive mechanisms and moreparticularly to a novel variable ratio rotary drive mechanism. Theinvention relates also to a wheel chair and chair wheel assemblyembodying the drive mechanism.

2. Prior Art As will appear from the ensuing description, the rotarydrive mechanism of the invention is capable of various uses andapplications. However, the drive mechanism is designed primarily for usein a wheel chair and will be described in this connection. Wheel chairsare widely used as a means of transportation by persons afflicted with agreat variety of different physical impairments. In some cases, whilethe affliction may require the patient to use a wheel chair,.it may notappreciably affect the strength of the patients arms and hands. In othercases, the patients arms and/or hands may be so weakened by hisparticular physical impairment as to render it extremely difficult orimpossible for thepatient to propel himself in a conventional wheelchair because of the substantial force which the patient mustexert onthewheels of the chair to move the latter.

Wheel chairs have been devised to alleviate this problem.

pose have wheel driving mechanisms which provide a mechanical advantagebut reduces the force which the occupant in the chair must exerttopropel the chair. These latter chairs, then, permit the patient topropel himself in a wheel chair with greater case, although at slowerspeed. The present invention is concerned with wheel chairs of thislatter class.

SUMMARY or THE INVENTION The present invention provides a variable ratiorotary drive mechanism having concentric driving and driven membersdefining an intervening annular space containing a variable ratio geartrain. This gear train drivably couples the members, whereby rotation ofone member drives the other member in rotation. According to animportant feature of the invention, a shift lever is provided foradjusting the ratio and hence mechanical advantage of the gear train.

The disclosed embodiment of the invention is a wheel chair having groundwheel assemblies each embodying a present variable ratio rotary drivemechanism. In this case, the outer member of the rotary drive mechanismin each wheel assembly is a driven cylindrical hub. The'inner member isa rotary driving shaft. Each wheel assembly further includes a wheel,with a mechanical advantage determined by the ratio of the gear train inthe drive mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation of a wheelchair having ground wheel assemblies which embody rotary drivemechanisms according to the invention;

FIG. 2 is an enlarged section taken on line 2-2 in FIG. 1;

FIG. 3 is an enlarged section taken on line 3-3 in FIG. 1 andillustrates the rotary drive mechanism adjusted for one speed ratio;

FIG. 4 is a fragmentary section similar to FIG. 3 illustrating the drivemechanism adjusted for another speed ratio;

FIG. 3 is a section taken on line 5-5 in FIG. 3; and

FIG. 6 is a section taken on line 6-6 in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to these drawings,there is illustrated a wheel chair 10 having a pair of ground wheelassemblies 12 (only one shown) each embodying a variable ratio rotarydrive mechanism 14 according to the invention. Turning to FIG. 3, itwill be observed that the present rotary drive mechanism 14 comprisesconcentric inner and outer members 16 and 18 defining an interveningannular space 20. Members I6 and 18 are drivably coupled by a variableratio transmission 22 in cluding a variable ratio gear train 24contained within the annular space 20. Accordingly, rotation of onemember drives the other member in rotation at a speed, and with amechanical advantage, determined by the ratio of the gear train. Thevariable ratio transmission 22 also includes a shift lever 26 which isoperable to vary the'ratio of the gear train 24 and thereby themechanical advantage of the variable ratio transmISSIOI'I.

In the particular embodiment of the invention which has been selectedfor illustration, the inner member 16,0f the rotary drive mechanism 14is a tubular rotary driving shaft and the outer member 18 is a rotarydrivencylindrical hub. This hub has annular sidewalls 28 and 30 joinedabout their perimeter by an intervening cylindrical rim 32. Extendingcentrally from the sidewall 30 is a cylindrical boss 34. Hub 18 isrotatably supported by bearings-36 and 38 on an axle 39. Bearing 36 ismounted within aIcent'ral opening in the hub wall 28. Bearing 38 ismounted within the hub wall boss 34. Shaft 16 is rotatable on the outerend of the axle 39 and extends through the outboard .bearingJiAxle 39has a length greater than the axial dimension of the hub 18 and isaxially positioned so that the ends of the axle project beyond the hubsidewalls 28 and 30, as shown.

In addition to the rotary-drive mechanism 14, each wheel assembly 12 ofthe wheel chair lOembodies a ground wheel 40 and a hand wheel 42. Theground wheel 40 surrounds, in concentric relation, the hub 18'and ismounted on the hub by means of spokes 44. The hand wheel 42 is keyed onand rigidly secured to the outer end of the shaft 16. The inner end ofthe axle 39 extends through aligned holes in a tubular member 46 of thechair frame and is secured to the frame by a nut 48. It will beunderstood that the two wheel assemblies 12 of the wheel chair 10 arelocated on a common axis and at opposite sides of the chair.

Briefly, in use of the wheel chair 10, the occupant of the chair rotatesthe hand wheels 42 to drive the ground wheels 40 through the variableratio gear trains 24 with a mechanical advantage determined by thesetting of the variable ratio transmissions 22. In theinventive'embodiments illustrated, each variable ratio transmission hastwo settings. In one setting, the driving shaft 16 is effectively keyeddirectly to the driven hub 18. The drive mechanism 14 then has a one toone drive ratio. In the other setting, the driving shaft 16 is coupledto the driven hub 18 through the geartrain 24. The drive mechanism thenhas a speed reduction ratio, whereby rotation of the shaft is effectiveto drive the hub with'a mechanical advantage.

Referring now in greater detail to the variable ratio transmission 22,the latter comprises a mounting plate 50 having a central hub 52 whichis slideable and rotatable on the wheel axle 39, just outwardly of theinboard wheel hub bearing shaft 16 is rotatably supported on the axle 39just outboard of the mounting plate 50 and extends outwardly along theaxle through the outboard wheel hub bearing 36 for attachment to thehand wheel 42. Slideable and rotatable on the inboard end of the drivingshaft 16 is a wheel drive plate 54. This drive plate has the elongateshape best shown in FIG. 5 and is formed at its diametrically opposedtips with gear sectors 56. Mounting plate 50 and drive plate 54 arerigidly joined by a number of connecting bolts or pins 58 to form acarriage. Two of these pins serve as journals for meshing pinions 60 and62. Inwardly formed on the inner wall of the cylindrical wheel hub rim32 are a pair of internal ring gears 64 and 66. An external gear 68 isintegrally formed on the inner end of the tubular driving shaft 16. Theradially outer pinion 60 meshes with the wheel hub ring gear 66. Theradially inner pinion 62 meshes with the driving shaft gear 68.

The mounting plate 50, drive plate 54, connecting pins 58, and pinions60, 62 collectively provide a gear assembly 70. This gear assembly isslideable and rotatable on the wheel axle 39. Gear assembly 70 ismovable axially relative to the wheel hub 18 between the positionsillustrated in FIGS. 3 and 4. For reasons which will appear presently,the position of the gear assembly shown in FIG. 3 is hereinafterreferred to as its low ratio or direct drive position. The positionillustrated in FIG. 4 is referred to as its high ratio or slow speedposition. During movement of the gear assembly between its direct driveand slow speed positions, the pinions 60, 62 slide back and forthrelative to but remain in meshing engagement with the wheel hub ringgear 66 and the driving shaft gear 68. In the direct drive position ofthe gear assembly 70, the gear sectors 56 on the drive plate 54 meshwith the wheel hub ring gear 64. The drive plate is then locked againstrotation relative to the driving shaft 16 by clutch means 72. Thisclutch means comprises drive pins 74 which are rigid on the drivingshaft 16 and engage in notches 76 in the drive plate54. It is obviousthat in this direct drive mode of the variable ratio transmission 22,the driving shaft 16 and hand wheel 42 are effectively keyed directly tothe wheel hub 18. Accordingly, rotation of the hand wheel drives theground wheel 40 with a direct, one to one drive ratio.

In the slow speed position ofthe gear assembly 70 shown in FIG. 4, thepinions 60, 62 remain in meshing engagement with the wheel hub ring gear66 and the driving shaft gear 68. The drive plate 54, however, isshifted to the right, out of engagement with the wheel hub ring gear 64.The mounting plate 50, and hence the drive plate 54, are locked to theaxle, and thus against rotation, by clutch means 78. This clutch meanscomprises elutch keys 80 rigid on the axle which engage in notches 82 inthe mounting plate hub 50. Under these conditions, rotation of the handwheel 42 drives the ground wheel 40 at reduced speed through the geartrain 68, 62, 60, 66 and with a mechanical advantage determined by theratio of the gear train.

The gear assembly 70 is shifted back and forth between its direct driveand slow speed positions by the shift means 26.1 this end, the shiftmeans comprises a yoke 84 having arms 86 which straddle the inner end 34of the wheel hub 18. Mounted on these arms are pins 88 which projectthrough slots 90 in the hub and engage in a circumferential groove 92 inthe mounting plate hub 52. Shift yoke 84 is pivoted on the wheel chairframe and is connected to a handle 94 in such a way that the gearassembly 70 may be shifted between its direct drive and slow speedpositions by means of the handle. A bracket 96 is provided on the wheelchair frame for locking the shift handle in its two positions.

It will be understood that the two wheel assemblies 12 of the wheelchair are substantially rnirror images of one another. Accordingly, theforegoing description may be considered as applying equally well to bothwheel assemblies. Each wheel as- While the invention has been disclosedin connection with a particular physical embodiment thereof, it will berecognized by those versed in the art that various modifications of theinvention are possible within the spirit and scope of the followingclaims.

We claim:

1. A wheel assembly for a wheel chair comprising: an axle, hub rotatableon said axle;

a ground wheel surrounding and mounted on said hub;

said axle having an end projecting beyond one end of said hub for rigidattachment to the frame of said wheel chair;

a tubular driving shaft rotatable on said axle and having one endprojecting beyond the opposite end of said hub;

a hand wheel fixed to said one end of said driving shaft;

a variable ratio gear transmission; and

said transmission comprising first and second axially spaced internalring gears in said hub, a sun gear rigid on said driving shaft, acarriage rotatable on and movable along said axle including a tootheddrive plate. Planetary pinion means rotatable on said carriage, saidcarriage being movable along said axle between a direct drive positionwherein the teeth on said drive plate mesh with said second ring gearand a slow speed position wherein said drive plate is disengaged fromsaid second ring gear and said pinion means mesh with said sun gear andfirst ring gear, first clutch means on said carriage and driving shaftagainst relative rotation in said direct drive position, and secondclutch means on said carriage and axle for locking said carriage andaxle against relative rotation in said slow speed position, and shiftmeans connected to said carriage including a handle accessible at theside of said wheel assembly adjacent said projecting end of said axlefor shifting said carriage between said positions.

2. A wheel chair comprising:

a chair frame; I

a pair of wheel assemblies at opposite sides, respectively, of saidframe each including an axle having an inner end rigidly secured to saidframe, a hub rotatable on said axle, a ground wheel surrounding andmounted on said hub, a tubular drive shaft rotatable on said axle andhaving an outer end projecting beyond the outer end of said hub, a handwheel fixed to the outer end of said drive shaft, a variable ratiotransmission within said hub drivably coupling said drive shaft and hub,and shift means accessible at the inner side of the respective wheel,assembly for adjusting the ratio of said transmission;

each transmission comprising first and second axially spaced internalring gears in said hub, a sun gear rigid on said driving shaft, acarriage rotatable on and movable along said axle including a tootheddrive plate, planetary pinion means rotatable on said carriage, saidcarriage being movable along said axle between a direct drive positionwherein the teeth on said drive plate mesh with said second ring gearand a slow speed position wherein said drive plate is disengaged fromsaid second ring gear and said pinion means mesh with said sun gear andfirst ring gear, first clutch means on said carriage and driving shaftagainst relative rotation in said direct drive position, and secondclutch means on said carriage and axle for locking said carriage andaxle against relative rotation in said slow speed position;

said shift means for each transmission comprising a handle connected tothe respective carriage for shifting the latter between its direct driveand slow speed positions; and the transmissions of said wheel assembliesbeing adjustable to provide said transmissions with equal first ratiosand equal second ratios differing from said first ratios.

1. A wheel assembly for a wheel chair comprising: an axle, hub rotatableon said axle; a ground wheel surrounding and mounted on said hub; saidaxle having an end projecting beyond one end of said hub for rigidattachment to the frame of said wheel chair; a tubular driving shaftrotatable on said axle and having one end projecting beyond the oppositeend of said hub; a hand wheel fixed to said one end of said drivingshaft; a variable ratio gear transmission; and said transmissioncomprising first and second axially spaced internal ring gears in saidhub, a sun gear rigid on said driving shaft, a carriage rotatable on andmovable along said axle including a toothed drive plate. Planetarypinion means rotatable on said carriage, said carriage being movablealong said axle between a direct drive position wherein the teeth onsaid drive plate mesh with said second ring gear and a slow speedposition wherein said drive plate is disengaged from said second ringgear and said pinion means mesh with said sun gear and first ring gear,first clutch means on said carriage and driving shaft against relativerotation in said direct drive position, and second clutch means on saidcarriage and axle for locking said carriage and axle against relativerotation in said slow speed position, and shift means connected to saidcarriage including a handle accessible at the side of said wheelassembly adjacent said projecting end of said axle for shifting saidcarriage between said positions.
 2. A wheel chair comprising: a chairframe; a pair of wheel assemblies at opposite sides, respectively, ofsaid frame each including an axle having an inner end rigidly secured tosaid frame, a hub rotatable on said axle, a ground wheel surrounding andmounted on said hub, a tubular drive shaft rotatable on said axle andhaving an outer end projecting beyond the outer end of said hub, a handwheel fixed to the outer end of said drive shaft, a variable ratiotransmission within said hub drivably coupling said drive shaft and hub,and shift means accessible at the inner side of the respective wheel,assembly for adjusting the ratio of said transmission; each transmissioncomprising first and second axially spaced internal ring gears in saidhub, a sun gear rigid on said driving shaft, a carriage rotatable on andmovable along said axle including a toothed drive plate, pLanetarypinion means rotatable on said carriage, said carriage being movablealong said axle between a direct drive position wherein the teeth onsaid drive plate mesh with said second ring gear and a slow speedposition wherein said drive plate is disengaged from said second ringgear and said pinion means mesh with said sun gear and first ring gear,first clutch means on said carriage and driving shaft against relativerotation in said direct drive position, and second clutch means on saidcarriage and axle for locking said carriage and axle against relativerotation in said slow speed position; said shift means for eachtransmission comprising a handle connected to the respective carriagefor shifting the latter between its direct drive and slow speedpositions; and the transmissions of said wheel assemblies beingadjustable to provide said transmissions with equal first ratios andequal second ratios differing from said first ratios.